Re: [streams] Move stuff into controller to make RS and RBS closer (#418)

Since some changes such as auto-release removal are not reflected to RBS yet, they don't looks very close yet. But except for them, they share most of code now.

To make it clear which operation is exposed to controller implementations, I've put some comments.

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Reply to this email directly or view it on GitHub:
https://github.com/whatwg/streams/pull/418#issuecomment-165550958